Archerd Shell Collection > Shell Classes > Gastropod Family Index > Blood Circulation

Blood and the Circulatory System in Gastropods

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General Circulation

Gastropods have a fairly well-organized circulatory system with heart, blood, a means of aerating the blood (gill or pallial lung), and a means of excreting salts that might accumulate (kidney). In the most primitive species, like abalones (Clade: Vetigastropoda), the circulatory system is bilaterally organized, with right and left paired organs; however, the much more numerous Prosobranchia have either lost the right side of each pair, or it has become vestigial.

(Left) The figure shows the circulatory anatomy of Littorina littorea, which is a representative model for most snails in the Clade, Littorinimorpha. Details vary, however,  among the numerous families comprising this clade (drawing adapted from Andrews & Taylor, 1988).

In the figure, blood is collected in the auricle then pumped by the ventricle of the heart at high pressure into an aorta. The aorta splits into an anterior fork (AA) supplying the foot and head and a posterior fork (PA) supplying the viscera.

Unlike vertebrates, there is no highly organized capillary system in either the head/foot or visceral regions. Instead, blood from the large vessels seeps through tissue spaces and accumulates in several sinuses (cavities). Then, it is  collected by large veins for return via the short portal vein to the kidney, before entering the gill.

After return through well organized blood vessels in the gill, blood enters the auricle of the heart. High pressure from the auricle forces an ultrafiltrate and soluble materials into the pericardial sac (PC --see small downward arrows). From the pericardial sac, a short duct leads ultrafiltrate to the kidney, where soluble materials may be either selectively reabsorbed or excreted to

the urine. Urine is discharged through a ureter, opening to the mantle cavity.

Marine gastropods are capable of regulating the ionic composition of their tissues through selective kidney reabsorption or excretion of calcium, potassium, magnesium and other ions, but in general they maintain an overall osmotic concentration near that of sea water. By comparison, land and freshwater gastropods exhibit a high degree of selectivity toward these ions and maintain rigorous osmotic control (Morton, 1979).

In many gastropods, the blood contains a faintly blue oxygen-binding pigment, hemocyanin. It functions like the red hemoglobin of mammals by facilitating oxygen transport to tissue cells. However, there are no blood corpuscles; rather, hemocyanin --or rarely hemoglobin-- exists simply dissolved in the blood plasma.

Archerd Shell Collection > Shell Classes > Gastropod Family Index > Blood Circulation